22 - Factors influencing liveweight in a range of network situations

J.H.H. MAEHL L. COULIBALY, A. DEFLY, G.D.M. d'IETEREN, A. FERON, G. GRUNDLER P. HACKER, P. ITTY, K. MAWUENA, G. MORKRAMER, M. MULUNGO, S.M. NAGDA, R. W. PALING, M. PELO, J.M. RARIEYA, A. SCHUETTERLE, M. SHERIA, W. THORPE and J.C.M. TRAIL

Introduction
Materials and methods
Results and discussion
Conclusion
References

Introduction

Liveweight traits are important components of the productivity of livestock. Yet, for livestock populations in the tsetse-affected areas of Africa, there are few estimates of the effects of trypanosome infection and its interaction with other environmental factors, on liveweight. The research of the ATLN is aimed at estimating the effects of trypanosome infection and other constraints on the health and performance of mainly trypanotolerant populations of cattle and sheep. Results on liveweight performance are presented here.

Materials and methods

The health and performance records of cattle and sheep used for this paper were collected over a three-year period, 1984-1986, at four Network sites. Three of the sites, Avetonou (Togo), Boundiali (Cote d'Ivoire) and Mushie (Zaire) were chosen because of their high mean trypanosome prevalence, and the fourth site, Kolo (Zaire), was chosen to give estimates of the liveweight performance of trypanotolerant cattle at zero trypanosomiasis risk. The four sites represent contrasting combinations of livestock species, breeds and management systems (Table 1). Site descriptions have been given in detail by ILCA (1986) and are summarized in article 3 of these Proceedings.

Table 1. Summary description of Network sites contributing to the analyses of liveweight performance.

Site	Mean Trypanosome prevalence (%)	Trypanosome species	Livestock		Management System
			Species	Breed	Ranch	Village
Avetonou	6.0	T. vivax	Cattle	N'Dama	X	X
				Race Locale	X	X
	3.0		Sheep	Djallonke		X
Boundiali	13.9	T. congolense and T. vivax	Cattle	N'Dama	X
				Baoule		X
				Crossesa		X
	9.2		Sheep	Djallonke		X
				Sahelian x
				Djallonke		X
Mushie	10.1	T. congolense and T. vivax	Cattle	N'Dama	X
Kolo	0.0	-	Cattle	N'Dama	X

^a Crosses between N'Dama, Baoule and Zebu.

The standardized Network protocol was used at all sites for the sequential recording at monthly intervals of body weights and health parameters (Murray et al., 1983). Health records included PCV, as a measure of anaemia level and the species and intensity of trypanosome infection detected by the dark/ground (DG) buffy coat method. Other systematic environmental factors were recorded as appropriate.

The liveweight traits on which the analyses were carried out were measured on dams and their pre-weaner progeny. The six traits were dam liveweights at parturition and weaning, dam liveweight change between parturition and weaning, progeny liveweights at birth and weaning and progeny pre-weaning daily gain. Weaning was defined as occurring at four and eight months post-partum in sheep and cattle, respectively. Comprehensive liveweight records were available on dams and pre-weaning progeny at all four sites, while post-weaner cattle were recorded only at Boundiali. Some results on cattle post-weaning liveweight traits are presented in article 12 of these Proceedings. This paper concentrates on dam and pre-weaner progeny performance.

Each site was analyzed separately by least-squares procedures (Harvey, 1977). Fixed-effect models included the factor of trypanosome infection which was quantified as the number of months during a, defined period in which trypanosomes were detected. The independent estimation of the effects of number and species of trypanosome infection was possible in some analyses. Infections in the dam during the gestation (five and nine months pre-partum in sheep and cattle, respectively) were evaluated for their effects on dam parturition weight and progeny birth weight and infections in the dam and her progeny during the pre-weaning period (four and eight months post-partum in sheep and cattle, respectively) were evaluated for their effects on dam and progeny liveweights at weaning and weight changes pre-weaning. Other factors included in the models were year/season of parturition/birth, dam breed, herd or location, dam age, offspring sex and the two factor interactions appropriate to a specific analysis in a given site. Possible relationships between liveweight and levels of anaemia were subsequently evaluated by substituting the effect of the number of trypanosome infections during a specific period by classes of mean PCV for the same period.

Results and discussion

Cattle

The least-squares means for the six liveweight traits at the four Network sites are presented in Table 2. Liveweights of these predominantly trypanotolerant cattle populations varied considerably between sites. For example mean cow liveweight post-partum and at weaning ranged from an average 228 kg for village cattle in Boundiali to 330 kg for ranch N'Dama at Kolo; the corresponding calf weaning weights were 86 kg and 129 kg, respectively. At Kolo, Mushie and Boundiali, cow weight change was only 2% or less of the mean parturition weight, while at Avetonou cows gained on average 7% of their parturition weight.

Table 2. Least-squares means and standard errors for six liveweight traits of trypanotolerant cattle at four Network sites.

Trait		Avetonou			Boundiali			Mushie			Kolo
		No.	Mean	s.e.	No.	Mean	s.e.	No.	Mean	s.e.	No.	Mean	s.e.
Cow
	Weight post-partum (kg)	179	261	4.6	102	224	4.9	305	301	1.8	438	3211	1.6
	Weight at weaning (kg)	173	271	5.1	142	231	5.3	361	274	2.5	553	332	1.11
	Weight change during lactation (g/d)	173	74	14.1	91	17	21.0	361	-18	9.2	553	15	6.3
Calf
	Birth weight (kg)	195	20.4	0.48	n.a.			405	24.9a	0.48	399	26.6a	0.29
	Weaning weight (kg)	112	117	2.9	96	116	3.5	299	113	1.4	432	129	1.2
	Pre-weaning growth (g/d)	112	394	14.6	96	179	15.0	299	386	5.8	432	445	6.0

^a At mean age of 10 days.

The statistical significance of the effects of trypanosome infection on these cow and calf liveweight traits are summarized in Table 3. Trypanosome infection significantly depressed the liveweight performance of N'Dama cattle at Mushie, but the effects at the other sites, although generally in the same direction as those at Mushie, did not reach statistical significance (P>0.05).

Table 3. Significance levels for the effect of trypanosome infection on cow and calf liveweight traits at Avetonou, Boundiali and Mushie.

Period of trypanosome infection	Trait	Avetonou	Boundiali	Mushie
In cow during gestation	Calf birth weighta	NS	-	*
	Cow weight post-partum	NS	NS	NS
In cow during lactation	Cow weight at weaning	NS	NS	NS
	Cow weight change during lactation	NS	NS	**
	Calf weaning weight	NS	NS	***
	Calf pre-weaning growth	NS	NS	*
In calf pre-weaning	Calf weaning weight	NS	NS	NS
	Calf pre-weaning growth	NS	NS	NS

^a period of infection 3 months pre-partum.
NS - not significant.
* - P<0.05
** - P<0.01
*** - p<0.001
(P values apply to all tables in this article unless otherwise indicated)

Table 4. Least-squares means and standard errors for birth-weight^a (kg) of calves born to N'Dama cows uninfected or infected with trypanosomes during three months pre partum, Mushie.

No. of trypanosome parasitaemias, 0-3 months pre-partum
	No.	Mean	s.e.
0	349	26.8	0.52
1 or more	56	22.9	1.71
Significance		*

^a At 10 days of age.

At Mushie trypanosome infection of the N'Dama cow during gestation did not affect her parturition weight, but if the infection occurred during the last three months pre-partum then the birth weight of her calf was depressed significantly by about 4 kg or 15% (Table 4). A similar effect on calf birth weight, although less pronounced, was observed at Avetonou. Calf birth weights were pot available for the Boundiali village cattle populations. No effect was observed when considering infections during the whole gestation. The lighter birth weight may reflect a depression of late foetal growth and/or result from premature birth. Records of conception dates are required to confirm the latter. Estimates of any effects on calf survival and pre- and post-weaning growth are also required.

The effect of the number of trypanosome infections during the eight month post-partum period on the liveweight performance of N'Dama cows is presented in Table 5. Uninfected cows could maintain liveweight but infected cows and especially those with two or more months with detectable parasitaemias, lost weight. These liveweight responses to infection post-partum were not affected by trypanosome infection during the preceding gestation.

Table 5. Least-squares means and standard errors for weaning weight (kg) and weight change (g/d) during lactation of N'Dama cows uninfected and infected post-partum with trypanosomes, Mushie.

No. of trypanosome parasitaemias 0-8 months post-partum	Cow weight at weaning (kg)		Cow weight change, during lactation (g/d)
	No.	Mean	s.e.	Mean	s.e.
0	182	279	3.0	9	11
1	89	274	3.4	-10	13
2 or more	90	272	3:4	-44	13
Significance	P<0.11			***

Table 6. Least-squares means and standard errors for cow weight change (g/d) during lactation of N'Dama cows uninfected by trypanosomes or infected by specific trypanosomes, Mushie.

Number and species of trypanosome parasitaemias, 0-8 months post partum	No.	Mean	s.e.
0	182	11	11
1 T. congolense	55	-12	16
1 T. vivax	34	-2	19
2 or more T. congolense	55	-39	16
2 or more T. vivax and mixed	35	-50	19
Significance	**

For these N'Dama cows at Mushie it was also possible to estimate the independent effects of number and species of trypanosome parasitaemias on weight change during lactation (Table 6). There was no consistent effect of trypanosome species within the classes of one and two or more parasitaemias suggesting that the number rather than the species of parasitaemia was the important factor affecting cow weight change.

Whereas the weight change during lactation of N'Dama cows in Mushie was affected by trypanosome infection, detectable trypanosome parasitaemia in the calf did not affect its pre-weaning growth (Table 7). However repeated trypanosome parasitaemia in the calf's dam during lactation did significantly depress the pre-weaning growth of the calf and the resultant weaning weight. Compared to the performance of calves reared by uninfected cows three or more detectable parasitaemias in the dam depressed calf pre-weaning growth by 11% and calf weaning weight by 7% (Table 7). In Avetonou trypanosome parasitaemia in the cow also tended to depress the weaning weight of its calf. At neither site was there a significant, nor apparently important, interaction between parasitaemia in the cow and in the calf.

Table 7. Least-squares means and standard errors for pre-weaning growth (g/d) and weaning weight (kg) of N'Dama calves uninfected or infected with trypanosomes and reared by dams uninfected or infected with trypanosomes during lactation, Mushie.

No. of trypanosome parasitaemias, 0-8 months post-partum		Calf pre-weaning growth (g/d)			Calf weaning weight (kg)
		No.	Mean	s.e.	Mean	s.e.
In the calf
	0	178	390	6.8	115	1.6
	1	72	381	10.7	112	2.5
	2 or more	49	387	11.6	114	2.7
	Significance		NS		NS
In the cow
	0	139	401	8.6	116	2.1
	1	77	403	9.4	118	2.2
	2	45	382	12.4	111	2.9
	3 or more	38	357	13.4	108	3.2
	Significance	*			***

In summary the results presented above would suggest that trypanosome infection is not a major factor affecting the liveweight performance of trypanotolerant cattle, but that when it does affect performance it does so in two ways. First, trypanosome infection of cows during the late gestation reduced calf birth weights. Whether these lighter birth weights were caused by reduced pre-natal growth within a normal gestation or were the result of premature births after a reduced gestation needs to be investigated. Second, it has been shown that cows infected during lactation weaned lighter calves, although parasitaemia in the calf did not directly affect the calf's own performance. This suggests that trypanosomiasis was affecting the dam's milk production. At the same time it was observed that cows infected during lactation not only weaned lighter calves but also lost body weight during that period, while uninfected cows were able to maintain weight, despite weaning heavier calves. This could suggest that the slower growth of calves reared by infected cows might be a result of a reduction in the availability of milk from infected cows, not necessarily because of reduced milk production per se, but perhaps due to poorer mothering behaviour.

These results for N'Dama cattle at Mushie, which were supported by similar trends at the other sites, need to be confirmed on large data sets. More also needs to be known about any cumulative effect of trypanosome infections on the liveweights of trypanotolerant and susceptible cattle types. Carefully designed studies will be required to quantify these effects and their interactions with breed and environmental factors, especially nutritional level.

Table 8. Significance levels for the effect of PCV class on cow and calf liveweight traits at four Network sites.

Period of average PCV	Trait	Avetonou	Boundiali	Mushie	Kolo
In cow during gestation	Calf birthwelghta	** (+)b	-	* (+)	*
	Cow weight post-partum	NS (-)	NS	NS (+)	NS
In cow during lactation	Cow weight at weaning	NS (+)	NS (+)	NS	***(+)
	Cow weight change during lactation	NS (+)	NS	* (+)	***(+)
	Calf weaning weight	NS (+)	NS	NS	***(-)
	Calf pre-weaning growth	NS (+)	NS	NS	***(-)
In calf pre-weaning	Calf weaning weight	NS (-)	P <.08 (+)	NS (+)	P <.07(+)
	Calf pre-weaning growth	NS (-)	* (+)	* (+)	NS (+)

^a Period of average PCV: 3 months pre-partum
^b Bracket indicates consistent positive or negative relation between PCV and liveweight.

Relationships between PCV and liveweight performance in cattle

Table 8 summarizes the results relating PCV and liveweight traits at the three sites, Avetonou, Boundiali and Mushie, where cattle were exposed to trypanosomiasis risk and at Kolo where N'Dama cattle were at no trypanosomiasis risk. Generally a low PCV was associated with poor liveweight performance and a high PCV with better performance. Table 9 presents the results relating mean PCV in the cow during the last three months pre-partum with calf birth weight. At Avetonou cows with PCVs of 33 or less gave birth to calves 2 kg lighter than cows with higher PCVs. Comparable results were obtained for N'Dama cattle at Mushie, whereas at Kolo there was no consistent relationship.

That PCV and liveweight performance may be related even in the absence of trypanosomiasis is illustrated in Table 10. Cow weight change during lactation was significantly related to mean PCV at both Mushie and Kolo, where cows with a PCV of over 30 and over 35%, respectively, were able to maintain or gain weight during lactation. The same trend was also observed in Avetonou, but at Boundiali the results were inconsistent.

Table 9. Least-squares means and standard errors of calf birthweight (kg) for classes of average PCV in the cow during the last three months of the gestation at three Network sites.

PCV	Avetonou			Mushie				Kolo
	No.	Mean	s.e.	PCV	No.	Meana	s.e.	PCV	No.	Meana	s.e.
<31	65	20.3	0.54	<29	90	25.5	0.70	<35	63	26.3	0.54
31-33	61	19.7	0.53	29-30	63	25.2	0.76	35-36	71	26.9	0.52
34-35	38	22.0	0.70	31-32	51	26.0	0.78	37	44	27.7	0.62
>35	37	22.1	0.72	33-34	58	26.0	0.77	38	39	26.9	0.66
				35-37	81	27.4	0.68	39	40	26.9	0.64
				>37	62	27.7	0,73	40	42	26.2	0.64
								>40	100	25.3	0.43
Significance	**			*				*

^a At mean age of 10 days.

Table 10. Least-squares means and standard errors of cow weight change (g/d) during lactation for classes of average PCV during lactation in N'Dama cows, Mushie and Kolo.

PCV	Mushie			Kolo
	No.	Mean	s.e.	PCV	No.	Mean	s.e.
<27	43	-57	18	<35	92	-21	12
27-28	61	-27	17	35	58	-7	14
29-30	61	-16	15	36	69	16	13
31-32	50	0	18	37	74	17	12
33-34	62	10	17	38	68	14	13
35-37	49	3	32	39	61	7	13
>37	37	82	53	40	54	25	14
				>40	77	67	12
Significance	*			***

Results from three sites showed a positive relationship of mean PCV in the calf pre-weaning with pre-weaning growth and weaning weight (Table 11).

No consistent positive relationship was found between cow PCV during lactation and calf liveweight traits, although as shown earlier in Table 7, trypanosome infection in the cow during lactation did depress calf liveweight traits.

Table 11. beast-squares means and standard errors of calf pre-weaning growth (g/d) and calf weaning weight (kg) for classes of average PCV in the calf pre-weaning at Boundiali, Mushie and Kolo.

PCV	Calf pre-weaning growth			Calf weaning weight
	No.	Mean	s.e.	Mean	s.e.
Boundiali
<30	9	157	25	82	6.1
30-31	41	173	15	87	3.7
32-33	31	188	16	86	3.9
>33	15	249	21	99	5.0
Significance	*			P<0.08
Mushie
<32	71	363	10	109	2.5
32-33	64	371	11	110	2.5
34-35	72	397	11	115	2.5
36-37	44	393	16	114	3.8
>37	48	419	20	118	4.8
Significance	*			NS
Kolo
<31	34	428	16	121	3.4
31	43	422	15	124	3.1
32	50	442	14	127	3.0
33	61	454	12	132	2.5
34	56	455	12	130	2.5
35	42	450	13	132	2.8
36	53	438	12	131	2.6
37	36	459	14	130	3.0
>37	57	462	12	135	2.6
Significance	NS			P<0.07

In summary it can be concluded that the present results from sites with different management systems and trypanosomiasis risk levels provide evidence for a positive relationship between PCV and liveweight performance, suggesting that PCV could well be used as an indicator of performance level. Further well-controlled experimental studies, such as that described by Trail et al. in paper 41 of these Proceedings will provide definitive information on the linkage between PCV and liveweight for cattle exposed to trypanosomiasis.

Other factors influencing liveweight performance of cattle

Year/season of parturition had an important effect on cow liveweight traits. Location or herd effects were important for cow and calf traits. For example in Avetonou liveweights were higher at the CREAT experimental ranch than in the herds in the surrounding villages. There was also large variation between village herds in Boundiali for cow weight at weaning which ranged from 206 to 262 kg and for calf weaning weight, which ranged from

63 to 100 kg. At Mushie ranch there was large variation between two distinct areas and between the herds within one of these areas. Cow age was also important, with older cows heavier at all sites, but only in Boundiali did they also wean heavier calves. Cow age had no effect on calf birth weight. As expected male weaner calves were heavier than females at all sites.

Sheep

The least-squares means for the liveweight traits obtained from separate analyses of the two sites are presented in Table 12. At the Avetonou site Djallonke ewes in village flocks had mean weights at parturition/weaning of 21 kg and lamb weaning weight averaged 9.3 kg. The corresponding means for the Djallonke population in the village flocks at the Boundiali site were 27 and 11.0 kg, some 20-30% heavier than the weights at Avetonou. At both sites ewes were able to maintain their body weight during the four months of lactation. Crossbreeding the Djallonke sheep with the Sahelian breed is of some importance in the Boundiali area and compared to pure Djallonke the small population of crosses had a 4% heavier mean ewe weight at parturition/weaning and 6% heavier lamb weaning weights (Table 12).

Table 12. Least-squares, means and standard errors for five liveweight bait' of sheep at Avetonou and Boundiali.

Trait		Avetonou			Boundiali
		Djallonke			Djallonke			Djallonke x Sahelian
		No.	Mean	s.e.	No.	Mean	s.e.	No.	Mean	s.e.
Ewe
	Weight post-partum (kg)	227	21.5	0.57	315	27.3	0.72	58	29.0	1.06
	Weight at weeping (kg)	199	20.8	0.42	334	26.7	0.45	65	27.4	0.80
	Weight change lactation (g/d)	lg.	5	3.0	334	1	3.4	65	6	6.1
Lamb
	Weaning weight at 4 months (kg)	178	9.3	0.21	173	11.0	1.13	40	11.7	0.67
	Pre-weaning daily gain (g)	178	55	2.9	173	70	5.1	40	80	11.3

Mean monthly trypanosome prevalence for sheep at Avetonou and Boundiali were 3.0 and 9.2%, respectively, during the three-year study period. Trypanosome infection in the ewe, as measured by the number of parasitaemic months during gestation and/or lactation, did not depress her subsequent body weight, nor was there any cumulative effect of trypanosome infection pre- and post-partum on ewe weight at weaning, nor on ewe weight change during the lactation. Similarly lamb weaning weight and lamb pre-weaning growth were not affected by one or more parasitaemic months in the ewe during lactation. Only the Djallonke population at Boundiali provided sufficient information to show that one or more trypanosome infections in the lamb did not depress lamb pre-weaning growth.

Relationships between PCV and liveweight traits for these sheep populations were generally inconsistent, although PCV levels in the lamb pre-weaning were positively related to lamb weaning weights at both Avetonou and Boundiali (P<0.01) (Table 13). A positive, although non-significant, relationship was also shown between ewe PCV during lactation and lamb weaning weight.

Table 13. Least-squares means and standard errors of lamb weaning weight at four months for classes of average lamb PCV pre-weaning, Avetonou and Boundiali.

Avetonou				Boundiali
PCV	No.	Mean	s.e.	PCV	No.	Mean	s.e.
<26	34	8.2	0.41	<26	43	9.5	0.63
26-28	39	8.3	0.36	26-28	56	10.9	0.59
29-31	60	9.5	0.29	29-31	66	11.7	0.47
>31	61	9.8	0.34	32-34	58	12.6	0.46
				>34	24	12.3	0.71

Sheep liveweight traits were generally more affected by other environmental factors than by trypanosome infection or PCV class. In Boundiali, for example, year/season of lambing and flock were statistically significant effects for all ewe and lamb liveweight traits. Age of ewe significantly affected ewe liveweight and litter size affected ewe weight post-partum and lamb weaning weight. Interactions between these effects and trypanosome infection or PCV were not important.

In summary ewe and lamb liveweight traits were not depressed by trypanosome infection occurring during the relatively short periods of gestation and/or lactation. However any possibly cumulative effects of trypanosome infection on sheep liveweight traits have still to be quantified, both for trypanotolerant and for susceptible sheep populations. Relationships with PCV as a potential indicator of performance level were found only for lamb weaning weight, but the apparent lack of a relationship needs to be confirmed. In contrast to the lack of an effect of trypanosome infection, other environmental factors were important influences affecting liveweight performance in these trypanotolerant populations.

Conclusion

The results from two Network sites have shown that trypanosome infection in Djallonke ewes and lambs did not affect their liveweight performances, at least in the short term. Nor was there any consistent relationship between PCV and liveweight except for lamb weaning weights. Factors other than trypanosome infection and PCV were more important sources of variation for liveweight performance in these trypanotolerant sheep populations.

For cattle, trypanosome infection did not significantly affect the liveweights of cows and calves in Avetonou and Boundiali. However in N'Dama cattle at Mushie, trypanosome infection in the cow significantly depressed calf birth weight, cow weight change during lactation and calf pre-weaning growth and weaning weight, but parasitaemia in the calf did not affect the calf's own growth. Trypanosome infection in the cow may therefore affect milk production. For cattle at trypanosomiasis risk it was shown that several liveweight traits were related to PCV, suggesting that PCV could be used as an indicator of liveweight performance for these populations.

Further studies are required to estimate, for all liveweight traits, the relative effects of T. vivax and T. congolense infections, as well as the effect of the intensity of parasitaemia. Additional analyses of the effects of trypanosome infection in the cow on calf birth weights, calf survival, calf growth and cow milk production should be concentrated on the period from three months pre-partum to the end of the lactation, as present results have shown no important effect of trypanosome infection during the earlier stages of the gestation. Studies are also required to estimate the effect of trypanosome infection on the post-weaning growth of cattle and sheep and to estimate any cumulative effects of trypanosome infection on dam liveweight and on the resultant herd and flock productivities. The designs of such future Network research should include the study of interactions between trypanosome infection and breed and nutritional level.

References

Harvey, W.R. 1977. User's Guide for Least-squares and Maximum Likelihood Computer Program. Columbus: Ohio State University.

ILCA. 1986. The ILCA/ILRAD Trypanotolerant Network. Situation Report, December 1985. Proceedings of a Network Meeting held at ILCA, Nairobi. ILCA, Addis Ababa.

Murray, M., J.C.M. Trail, D.A. Turner and Y. Wissocq. 1983. Livestock Productivity and Trypanotolerance. Network Training Manual. Addis Ababa: ILCA.